# Names of Symbols and Mathematical Objects

*Mathematica* by default interprets any sequence of letters or letter-like forms as the name of a symbol.

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form | character name | alias | interpretation |

\[Pi] | EscpEsc, EscpiEsc | equivalent to Pi | |

\[Infinity] | EscinfEsc | equivalent to Infinity | |

\[ExponentialE] | EsceeEsc | equivalent to E | |

\[ImaginaryI] | EsciiEsc | equivalent to I | |

\[ImaginaryJ] | EscjjEsc | equivalent to I |

Symbols with built-in meanings whose names do not start with capital English letters.

Essentially all symbols with built-in meanings in *Mathematica* have names that start with capital English letters. Among the exceptions are and , which correspond to E and I respectively.

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In written material, it is standard to use very short names—often single letters—for most of the mathematical objects that one considers. But in *Mathematica*, it is usually better to use longer and more explicit names.

In written material you can always explain that a particular single-letter name means one thing in one place and another in another place. But in *Mathematica*, unless you use different contexts, a global symbol with a particular name will always be assumed to mean the same thing.

As a result, it is typically better to use longer names, which are more likely to be unique, and which describe more explicitly what they mean.

For variables to which no value will be assigned, or for local symbols, it is nevertheless convenient and appropriate to use short, often single-letter, names.

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form | input | interpretation |

x_{n} | x Ctrl+_ n Ctrl+Space | Subscript[x,n] |

x_{+} | x Ctrl+_ + Ctrl+Space | SubPlus[x] |

x_{-} | x Ctrl+_ - Ctrl+Space | SubMinus[x] |

x_{*} | x Ctrl+_ * Ctrl+Space | SubStar[x] |

x^{+} | x Ctrl+^ + Ctrl+Space | SuperPlus[x] |

x^{-} | x Ctrl+^ - Ctrl+Space | SuperMinus[x] |

x^{*} | x Ctrl+^ * Ctrl+Space | SuperStar[x] |

x^{†} | x Ctrl+^ EscdgEsc Ctrl+Space | SuperDagger[x] |

x Ctrl+& _ Ctrl+Space | OverBar[x] | |

x Ctrl+& EscvecEsc Ctrl+Space | OverVector[x] | |

x Ctrl+& ~ Ctrl+Space | OverTilde[x] | |

x Ctrl+& ^ Ctrl+Space | OverHat[x] | |

x Ctrl+& . Ctrl+Space | OverDot[x] | |

x Ctrl++ _ Ctrl+Space | UnderBar[x] | |

x | Style[x,Bold] | x |

Creating objects with annotated names.

Note that with a notebook front end, you can change the style of text using menu items.

option | typical default value | |

SingleLetterItalics | False | whether to use italics for single-letter symbol names |

MultiLetterItalics | False | whether to use italics for multi-letter symbol names |

SingleLetterStyle | None | the style name or directives to use for single-letter symbol names |

MultiLetterStyle | None | the style name or directives to use for multi-letter symbol names |

Options for cells in a notebook.

It is conventional in traditional mathematical notation that names consisting of single ordinary English letters are normally shown in italics, while other names are not. If you use TraditionalForm, then *Mathematica* will by default follow this convention. You can explicitly specify whether you want the convention followed by setting the SingleLetterItalics option for particular cells or cell styles. You can further specify styles for names using single English letters or multiple English letters by specifying values for the options and .